5.23. Spray drying is a process in which a liquid containing dissolved or suspended solids is injected into a chamber through a spray nozzle or centrifugal disk atomizer. The resulting mist is contacted with hot air, which evaporates most or all of the liquid, leaving the dried solids to fall to a conveyor belt at the bottom of the chamber. Milk (70% H,O) Wet air 311 m’/min @ 83°C, 1 atm Dried milk Inlet air 167°C, -40 cm H,O Powdered milk is produced in a spray dryer 6 m in diameter by 6 m high. Air enters at 167°C and -40 cm H,O. The milk fed to the atomizer contains 70% water by mass, all of which evaporates. The outlet gas contains 12 mole% water and leaves the chamber at 83°C and 1 atm (absolute) at a rate of 311 m/min. (a) Calculate the production rate of dried milk and the volumetric flow rate of the inlet air. Estimate the upward velocity of air (m/s) at the bottom of the dryer. (b) Engineers often face the challenge of what to do to a process when demand for a product increases (or decreases). Suppose in the present case production must be doubled. (i) Why is it unlikely that the flow rates of feed and air can simply be increased to achieve the new production rate? (ii) An obvious option is to buy another dryer like the existing one and operate the two in parallel. Give two advantages and two disadvantages of this option. (ii) Still another possibility is to buy a larger dryer to replace the original unit. Give two advantages and two disadvantages of doing so. Estimate the approximate dimensions of the larger unit.
5.23. Spray drying is a process in which a liquid containing dissolved or suspended solids is injected into a chamber through a spray nozzle or centrifugal disk atomizer. The resulting mist is contacted with hot air, which evaporates most or all of the liquid, leaving the dried solids to fall to a conveyor belt at the bottom of the chamber. Milk (70% H,O) Wet air 311 m’/min @ 83°C, 1 atm Dried milk Inlet air 167°C, -40 cm H,O Powdered milk is produced in a spray dryer 6 m in diameter by 6 m high. Air enters at 167°C and -40 cm H,O. The milk fed to the atomizer contains 70% water by mass, all of which evaporates. The outlet gas contains 12 mole% water and leaves the chamber at 83°C and 1 atm (absolute) at a rate of 311 m/min. (a) Calculate the production rate of dried milk and the volumetric flow rate of the inlet air. Estimate the upward velocity of air (m/s) at the bottom of the dryer. (b) Engineers often face the challenge of what to do to a process when demand for a product increases (or decreases). Suppose in the present case production must be doubled. (i) Why is it unlikely that the flow rates of feed and air can simply be increased to achieve the new production rate? (ii) An obvious option is to buy another dryer like the existing one and operate the two in parallel. Give two advantages and two disadvantages of this option. (ii) Still another possibility is to buy a larger dryer to replace the original unit. Give two advantages and two disadvantages of doing so. Estimate the approximate dimensions of the larger unit.
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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Transcribed Image Text:5.23. Spray drying is a process in which a liquid containing dissolved or suspended solids is injected into a
chamber through a spray nozzle or centrifugal disk atomizer. The resulting mist is contacted with hot
air, which evaporates most or all of the liquid, leaving the dried solids to fall to a conveyor belt at the
bottom of the chamber.
Milk (70% H,O)
Wet air
311 m’/min @ 83°C, 1 atm
Dried milk
Inlet air
167°C, -40 cm H,O
Powdered milk is produced in a spray dryer 6 m in diameter by 6 m high. Air enters at 167°C
and -40 cm H,O. The milk fed to the atomizer contains 70% water by mass, all of which
evaporates. The outlet gas contains 12 mole% water and leaves the chamber at 83°C and 1 atm
(absolute) at a rate of 311 m/min.
(a) Calculate the production rate of dried milk and the volumetric flow rate of the inlet air. Estimate
the upward velocity of air (m/s) at the bottom of the dryer.
(b) Engineers often face the challenge of what to do to a process when demand for a product increases
(or decreases). Suppose in the present case production must be doubled. (i) Why is it unlikely that
the flow rates of feed and air can simply be increased to achieve the new production rate? (ii) An
obvious option is to buy another dryer like the existing one and operate the two in parallel. Give
two advantages and two disadvantages of this option. (ii) Still another possibility is to buy a
larger dryer to replace the original unit. Give two advantages and two disadvantages of doing so.
Estimate the approximate dimensions of the larger unit.
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